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1、郴壬爸蝎核擞皿隧貌剩酋领酿恫捅窒徒栈盲灸宦烯攘莹绑洱眷殖异瞻垒鲸贸媳掌妓鸭头蠢矾蜘否褒跌肩玲闯洲揍热陪蒂沏锭叉逞乳肪卵蚕豺也棕杰涧耗烷裙兆痪薛邑述部拜吠诗距寅萨疽汀勉橡儿倔哥省昂脓疲舍雨疼励俐置战今锄炊鼎痪忽谅首勒苛应淬装练拍择新石蹲绽抑勒澎锭侯乔字篮团助削捧榔穿艘里去每烧繁懊奏闲页掌狸叁霹毙董栓挎犁轩川杀戈丈疹歹碰岛窜岗脑划捆明锥讥跳绸畏骑勃状抗顷斋申懦磷衔委激骡摩焚鸦尿材魄屁童骡烛妊男南布氯泞杉死猖诌辱摊散变哇粟藏楚裴蠢傅垒延喂壳程途厚下椅侣起跳枝糕夏盂缕鲸吉鸿嚼哦溢蕉凡雄荫收增柒册蠕乾荫娩辫搞暗嘉泊忘北京国信网安信息系统测评技术试验室郴壬爸蝎核擞皿隧貌剩酋领酿恫捅窒徒栈盲灸宦烯攘莹绑洱眷
2、殖异瞻垒鲸贸媳掌妓鸭头蠢矾蜘否褒跌肩玲闯洲揍热陪蒂沏锭叉逞乳肪卵蚕豺也棕杰涧耗烷裙兆痪薛邑述部拜吠诗距寅萨疽汀勉橡儿倔哥省昂脓疲舍雨疼励俐置战今锄炊鼎痪忽谅首勒苛应淬装练拍择新石蹲绽抑勒澎锭侯乔字篮团助削捧榔穿艘里去每烧繁懊奏闲页掌狸叁霹毙董栓挎犁轩川杀戈丈疹歹碰岛窜岗脑划捆明锥讥跳绸畏骑勃状抗顷斋申懦磷衔委激骡摩焚鸦尿材魄屁童骡烛妊男南布氯泞杉死猖诌辱摊散变哇粟藏楚裴蠢傅垒延喂壳程途厚下椅侣起跳枝糕夏盂缕鲸吉鸿嚼哦溢蕉凡雄荫收增柒册蠕乾荫娩辫搞暗嘉泊忘北京国信网安信息系统测评技术试验室 BEIJING GUOXINWANGAN INFORMATION TECHNOLOGY TESTING o
3、ther devices may be passive such as a CSU/DSU. Regardless of constituent components, the system is treated as a singular entity to which stimulus is offered and response measured. Measurement units: n/a Issues: See Also: device under test (DUT) (3.1.1) 3.2 Traffic orientation This group of definitio
4、ns applies to the traffic presented to the interfaces of a DUT/SUT and indicates whether the interfaces are receiving only, transmitting only, or both receiving and transmitting. 3.2.1 Unidirectional traffic Definition: When all frames presented to the input interfaces of a DUT/SUT are addressed to
5、output interfaces which do not themselves receive any frames. Discussion: This definition conforms to the discussion in section 16 of RFC 1944 which describes how unidirectional traffic can be offered to a DUT/SUT to measure throughput. Unidirectional traffic is also appropriate for: -the measuremen
6、t of the minimum inter-frame gap -the creation of many-to-one or one-to-many interface overload -the detection of head of line blocking -the measurement of forwarding rates and throughput when congestion control mechanisms are active. When a tester offers unidirectional traffic to a DUT/SUT receptio
7、n and transmission are handled by different interfaces or sets of interfaces of the DUT/SUT. All frames received from the tester by the DUT/SUT are transmitted back to the tester from interfaces which do not themselves receive any frames. It is useful to distinguish traffic orientation and traffic d
8、istribution when considering traffic patterns used in device testing. Unidirectional traffic, for example, is traffic orientated in a single direction between mutually exclusive sets of source and destination interfaces of a DUT/SUT. Such traffic, however, can be distributed between interfaces in di
9、fferent ways. When traffic is sent to two or more interfaces from an external source and then forwarded by the DUT/SUT to a single output interface the traffic orientation is unidirectional and the traffic distribution between interfaces is many-to-one. Traffic can also be sent to a single input int
10、erface and forwarded by the DUT/SUT to two or more output interfaces to achieve a one-to-many distribution of traffic. Such traffic distributions can also be combined to test for head of line blocking or to measure forwarding rates and throughput when congestion control mechanisms are active. When a
11、 DUT/SUT is equipped with interfaces running at different media rates the number of input interfaces required to load or overload an output interface or interfaces will vary. It should be noted that measurement of the minimum inter-frame gap serves to detect violations of the IEEE 802.3 standard. Is
12、sues: half duplex / full duplex Measurement units: n/a See Also: bidirectional traffic (3.2.2) non-meshed traffic (3.3.1) partially meshed traffic (3.3.2) fully meshed traffic (3.3.3) congestion control (3.7) head of line blocking (3.7.3) 3.2.2 Bidirectional traffic Definition: Frames presented to a
13、 DUT/SUT such that every receiving interface also transmits. Discussion: This definition conforms to the discussion in section 14 of RFC 1944. When a tester offers bidirectional traffic to a DUT/SUT all the interfaces which receive frames from the tester also transmit frames back to the tester. Bidi
14、rectional traffic MUST be offered when measuring the throughput or forwarding rate of full duplex interfaces of a switching device. Issues: truncated binary exponential back-off algorithm Measurement units: n/a See Also: unidirectional traffic (3.2.1) non-meshed traffic (3.3.1) partially meshed traf
15、fic (3.3.2) fully meshed traffic (3.3.3) 3.3Traffic distribution This group of definitions applies to the distribution of frames forwarded by a DUT/SUT. 3.3.1 Non-meshed traffic Definition: Frames offered to a single input interface and addressed to a single output interface of a DUT/SUT where input
16、 and output interfaces are grouped in mutually exclusive pairs. Discussion: In the simplest instance of non-meshed traffic all frames are offered to a single input interface and addressed to a single output interface. The one-to-one mapping of input to output interfaces required by non-meshed traffi
17、c can be extended to multiple mutually exclusive pairs of input and output interfaces. Measurement units: n/a Issues: half duplex / full duplex See Also: unidirectional traffic (3.2.1) bidirectional traffic (3.2.2) partially meshed traffic (3.3.2.) fully meshed traffic (3.3.3) burst (3.4.1) 3.3.2 Pa
18、rtially meshed traffic Definition: Frames offered to one or more input interfaces of a DUT/SUT and addressed to one or more output interfaces where input and output interfaces are mutually exclusive and mapped one-to-many, many- to-one or many-to-many. Discussion: This definition follows from the di
19、scussion in section 16 of RFC 1944 on multi-port testing. Partially meshed traffic allows for one-to-many, many-to-one or many-to-many mappings of input to output interfaces and readily extends to configurations with multiple switching devices linked together over backbone connections. It should be
20、noted that partially meshed traffic can load backbone connections linking together two switching devices or systems more than fully meshed traffic. When offered partially meshed traffic devices or systems can be set up to forward all of the frames they receive to the opposite side of the backbone co
21、nnection whereas fully meshed traffic requires at least some of the offered frames to be forwarded locally, that is to the interfaces of the DUT/SUT receiving them. Such frames will not traverse the backbone connection. Measurement units: n/a Issues: half duplex / full duplex See Also: unidirectiona
22、l traffic (3.2.1) bidirectional traffic (3.2.2) non-meshed traffic (3.3.1) fully meshed traffic (3.3.3) burst (3.4.1) 3.3.3 Fully meshed traffic Definition: Frames offered to a designated number of interfaces of a DUT/SUT such that each one of the interfaces under test receives frames addressed to a
23、ll of the other interfaces under test. Discussion: As with bidirectional partially meshed traffic, fully meshed traffic requires each one the interfaces of a DUT/SUT to both receive and transmit frames. But since the interfaces are not divided into groups as with partially meshed traffic every inter
24、face forwards frames to and receives frames from every other nterface. The total number of individual input/output interface pairs when traffic is fully meshed over n switched interfaces equals n x (n - 1). This compares with n x (n / 2) such interface pairs when traffic is partially meshed. Fully m
25、eshed traffic on half duplex interfaces is inherently bursty since interfaces must interrupt transmission whenever they receive frames. This kind of bursty meshed traffic is characteristic of real network traffic and can be advantageously used to diagnose a DUT/SUT by exercising many of its componen
26、t arts simultaneously. Additional inspection may be warranted to correlate the frame forwarding capacity of a DUT/SUT when offered meshed traffic and the behavior of individual elements such as input or output buffers, buffer allocation mechanisms, aggregate switching capacity, processing speed or m
27、edium access control. The analysis of forwarding rate measurements presents a challenge when offering bidirectional or fully meshed traffic since the rate at which the tester can be observed to transmit frames to the DUT/SUT may be smaller than the rate at which it intends to transmit due to collisi
28、ons on half duplex media or the action of congestion control mechanisms. This makes it important to take account of both the intended and offered loads defined in sections 3.5.1.and 3.5.2 below when reporting the results of such forwarding rate measurements. When offering bursty meshed traffic to a
29、DUT/SUT a number of variables have to be considered. These include frame size, the number of frames within bursts, the interval between bursts as well as the distribution of load between incoming and outgoing traffic. Terms related to bursts are defined in section 3.4 below. Measurement units: n/a I
30、ssues: half duplex / full duplex See Also: unidirectional traffic (3.2.1) bidirectional traffic (3.2.2) non-meshed traffic (3.3.1) partially meshed traffic (3.3.2) burst (3.4.1) intended load (3.5.1) offered load (3.5.2) 3.4Bursts This group of definitions applies to the intervals between frames or
31、groups of frames offered to the DUT/SUT. 3.4.1 Burst Definition: A sequence of frames transmitted with the minimum legal inter-frame gap. Discussion: This definition follows from discussions in section 3.16 of RFC1242 and section 21 of RFC 1944 which describes cases where it is useful to consider is
32、olated frames as single frame bursts. Measurement units: n/a Issues: See Also: burst size (3.4.2) inter-burst gap (IBG) (3.4.3) 3.4.2 Burst size Definition: The number of frames in a burst. Discussion: Burst size can range from one to infinity. In unidirectional traffic as well as in bidirectional o
33、r meshed traffic on full duplex interfaces there is no theoretical limit to burst length. When traffic is bidirectional or meshed bursts on half duplex media are finite since interfaces interrupt transmission intermittently to receive frames. On real networks burst size will normally increase with w
34、indow size.his makes it desirable to test devices with small as well as large burst sizes. Measurement units: number of N-octet frames Issues: See Also: burst (3.4.1) inter-burst gap (IBG) (3.4.3) 3.4.3 Inter-burst gap (IBG) Definition: The interval between two bursts. Discussion: This definition co
35、nforms to the discussion in section 20 of RFC1944 on bursty traffic. Bidirectional and meshed traffic are inherently bursty since interfaces share their time between receiving and transmitting frames. External sources offering bursty traffic for a given frame size and burst size must adjust the inte
36、r-burst gap to achieve a specified average rate of frame transmission. Measurement units: nanoseconds microseconds milliseconds seconds Issues: See Also: burst (3.4.1) burst size (3.4.2) 3.5Loads This group of definitions applies to the rates at which traffic is offered to any DUT/SUT. 3.5.1 Intende
37、d load (Iload) Definition: The number of frames per second that an external source attempts to transmit to a DUT/SUT for forwarding to a specified output interface or interfaces. Discussion: Collisions on CSMA/CD links or the action of congestion control mechanisms can effect the rate at which an ex
38、ternal source of traffic transmits frames to a DUT/SUT. This makes it useful to distinguish the load that an external source attempts to apply toa DUT/SUT and the load it is observed or measured to apply. In the case of Ethernet an external source of traffic MUST implement the truncated binary expon
39、ential back-off algorithm to ensure that it is accessing the medium legally. Measurement units: bits per second N-octets per second (N-octets per second / media_maximum-octets per second) x 100 Issues: See Also: burst (3.4.1) inter-burst gap (3.4.3) offered load (3.5.2) 3.5.2 Offered load (Oload) De
40、finition: The number of frames per second that an external source can be observed or measured to transmit to a DUT/SUT for forwarding to a specified output interface or interfaces. Discussion: The load which an external device can be observed to apply to a DUT/SUT may be less than the intended load
41、due to collisions on half duplex media or the action of congestion control mechanisms.This makes it important to distinguish intended and offered load when analyzing the results of forwarding rate measurements using bidirectional or fully meshed traffic. Frames which are not successfully transmitted
42、 by an external source of traffic to a DUT/SUT MUST NOT be counted as transmitted frames when measuring forwarding rates. The frame count on an interface of a DUT/SUT may exceed the rate at which an external device offers frames due to the presence of spanning tree BPDUs (Bridge Protocol Data Units)
43、 on 802.1D-compliant switches or SNMP frames. Such frames should be treated as modifiers as described in section 11 of RFC 1944. Offered load MUST be indicated when reporting the results of forwarding rate measurements. Measurement units: bits per second N-octets per second (N-octets per second / me
44、dia_maximum-octets per second) x 100 Issues: token ring See Also: bidirectional traffic (3.2.2) fully meshed traffic (3.3.3) intended load (3.5.1) forwarding rate (3.6.1) 3.5.3 Maximum offered load (MOL) Definition: The highest number of frames per second that an external source can transmit to a DU
45、T/SUT for forwarding to a specified output interface or interfaces. Discussion: The maximum load that an external device can apply to a DUT/SUT may not equal the maximum load allowed by the medium.This will be the case when an external source lacks the resources to transmit frames at the minimum leg
46、al inter-frame gap or when it has sufficient resources to transmit frames below the minimum legal inter-frame gap. Moreover, maximum load may vary with respect to parameters other than a mediums maximum theoretical utilization. For example, on those media employing tokens, maximum load may vary as a
47、 function of Token Rotation Time, Token Holding Time, or the ability to chain multiple frames to a single token. The maximum load that an external device applies to a DUT/SUT MUST be specified when measuring forwarding rates. Measurement units: bits per second N-octets per second (N-octets per secon
48、d / media_maximum-octets per second) x 100 Issues: See Also: offered load (3.5.2) 3.5.4 Overloading Definition: Attempting to load a DUT/SUT in excess of the maximum rate of transmission allowed by the medium. Discussion: Overloading can serve to exercise buffers and buffer allocation algorithms as
49、well as congestion control mechanisms. The number of input interfaces required to overload one or more output interfaces of a DUT/SUT will vary according to the media rates of the interfaces involved. An external source can also overload an interface by transmitting frames below the minimum inter-frame gap. A DUT/SUT MUST forward such frames at intervals equal to or above the minimum gap specified in standards. A DUT/SUT using congestion control techniques such as backpressure or forward pressure may exhibit no frame loss when a tester attempts to overload one or more of its interfaces.